Launched missiles typically employ combustible rocket motor propellants which generate high temperature gases in their exhaust plumes, thus subjecting the launch platform to a hazardous and destructive environment upon deployment of the missile. The problem can be particularly acute for personnel-held launch platforms, such as shoulder-launched missiles, where the temperatures and gases associated with the exhaust plume can create unsafe conditions. Further, the noise level generated by rocket motor propellants during missile launch is also very high. The potentially unsafe conditions are exacerbated when a shoulder-launched missile is operated from a confined or enclosed area, thereby also subjecting the operator to the toxic gases of the missile exhaust. High temperature exhaust gases can also damage the launch platform. Moreover, the high temperature exhaust plumes exhibit a high infrared signature, thereby potentially betraying the position of the launch platform in a hostile environment.
Consequently, it is necessary that the launch platform be protected or rebuilt after a launch, and/or that the operator use protective equipment, both to protect the hearing and also to prevent the operator from being burned by the exhaust plume of the missile as it leaves the launch platform.
Eject motors have been used to avoid some of the problems described above. An eject motor is a secondary propulsion device that attaches to a missile having a primary propulsion motor which employs combustible rocket motor propellants. The eject motor propels the missile from its launch platform using a propellant that creates less noise, toxic gases, heat, and/or smoke than the primary rocket motor propellant. When the missile is a safe distance from the launch platform and the operator, the primary propulsion motor is ignited. Conventionally, eject motors using reduced smoke propellants have been used as a means for initiating the missile launch sequence by propelling the missile from the launch platform prior to ignition of the primary propulsion motor. Typical reduced smoke propellants develop large amounts of carbon monoxide and hydrochloric acid gases, which can be hazardous to an operator and further have readily detectable infrared emissions.
The above-described disadvantages associated with prior rocket eject motors are avoided in accordance with the present invention, which relates to an eject motor to be coupled to a missile that is launched from a launch platform structure and is propelled by ignited combustible rocket motor propellant. The eject motor initiates a launch sequence of the missile by propelling the missile from the launch platform structure prior to ignition of the combustible rocket motor propellant. In accordance with the present invention, the eject motor comprises a case including a structure for coupling the case to the missile, an ignitable gas generant material stored in the case, a generant screen disposed within the case for retaining the ignitable gas generant material within the case, an igniter mechanism constructed and arranged to ignite the ignitable gas generant material, the ignitable gas generant material generating combustion gases when ignited, and a nozzle secured to the case and constructed and arranged to focus and direct combustion gases generated by the ignitable gas generant material to create a thrust acting on the missile to which the eject motor is coupled to propel the missile from the launch platform structure.
Gas generants used in the eject motor, which may be the same as those used in automotive airbag inflators, produce non-toxic combustion gases which are cooler than the exhaust gases from conventional rocket propellants. Like an automotive air bag inflator, the eject motor of the present invention employs a screen pack to retain condensable combustion products and to reduce noise levels generated during operation of the eject motor.
Conventional rocket motor propellants typically do not completely oxidize during engine bum and thus often experience a secondary burn outside the rocket engine housing. Gas generant propellants, on the other hand, do completely oxidize during combustion and thus do not experience after burning, or secondary burning, outside the rocket engine housing. Moreover, gas generant propellants typically combust with lower flame temperatures than conventional rocket motor propellants. Thus, due to the lack of after burning and the lower flame temperatures, the exhaust products of gas generants generally produce less of an infrared signature when compared to exhaust products of conventional rocket motor propellants. Moreover, as opposed to the toxic gases produced by primary rocket propellants and reduced smoke propellants, gas generants produce primarily H2O, N2, and some CO2 gas.
Other objects, features, and characteristics of the present invention, as well as the methods of operation of the invention and the function and interrelation of the elements of structure, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this disclosure, wherein like reference numerals designate corresponding parts in the various figures.